1. Field of the Invention
This invention relates to an audio system using a plurality of speakers to create a high-quality sound field space, and more particularly to a technique for automatically detecting state of speaker connection to the audio system.
2. Description of Related Art
For an audio system to provide a high-quality sound field space, it is required to automatically create a sound field space with presence by using a plurality of speakers. Therefore, it is necessary to set the configuration of the speaker system used in the audio system, in advance, in the audio system.
Conventionally, a user connects a plurality of speakers to the audio system and then manually inputs the speaker system configuration to the audio system.
As a method of automatically detecting the speaker system configuration, it is conceivable to detect impedance variation of the audio system viewed from the side of the amplifier in the audio system so that the audio system can automatically detect the presence or absence of the speaker. Namely, since the impedance of the audio system viewed from the amplifier side changes according to the presence or absence of the speaker connected, the presence or absence of the speaker can be detected by detecting the impedance variation in the case a predetermined test signal is output. However, the above-described method requires an exclusive hardware to detect the presence or absence of the speaker.
It is an object of the present invention to provide a speaker detecting device capable of automatically detecting speakers connected to the audio system, without being affected by environmental noise.
According to one aspect of the present invention, there is provided a speaker detecting device including: an output terminal for outputting a signal to drive a speaker; a test signal supplying unit for supplying the test signal to the output terminal; a test sound detecting unit, installed in an acoustic space in which the speaker is installed, for detecting a test sound corresponding to the test signal; and a speaker existence judging unit for judging whether or not a speaker is connected to the output terminal by comparing a signal level of the test sound, detected by the test sound detecting unit when the test signal supplying unit supplies the test signal to the output terminal, with a predetermined threshold level.
According to the speaker detecting device thus configured, the test signal is supplied to the output terminal to which the speaker is to be connected. If a speaker is connected to the output terminal, the test sound is output via the speaker. If no speaker is connected to the output terminal, no test sound is output. The test sound detecting unit detects the test sound in the acoustic space and compares the signal level of the test sound with the predetermined threshold level, thereby to judge whether or not a speaker is connected to the output terminal.
The speaker detecting device may further include: an environmental noise detecting unit for detecting environmental noise in the acoustic space; and an optimum frequency band determining unit for determining an optimum frequency band of the test signal by analyzing a level of the environmental noise in terms of spectrum. In that case, the speaker existence judging unit may compare the level of the signal in the optimum frequency band, out of the signals detected by the test sound detecting unit, with the predetermined threshold level. By this, since the optimum frequency band is determined based on the spectrum analysis of the environmental noise, the speaker existence can be judged by using the frequency band with small environmental noise.
The optimum frequency band determining unit may determine the frequency band having a highest acoustic S/N ratio as the optimum frequency band. Thus, the accuracy in the speaker existence detection may be improved.
The optimum frequency band determining unit may include: a unit for storing a predetermined signal curve data; a unit for detecting the level of the environmental noise detected by the environmental noise detecting unit for each of multiple frequency bands to produce a noise curve data; and a unit for determining the frequency band having the highest acoustic S/N ratio as the optimum frequency band by comparing the curve data with the noise curve data. With this configuration, since the optimum frequency band is determined based on the signal curve data determined in consideration of auditory sensitivity of human being and the environmental noise data, it is possible to prevent a person in the acoustic space from feeling uncomfortable by the test sound.
The speaker detecting device may further include a threshold level setting unit for setting a level between the signal curve data and the noise curve data in the optimum frequency band to the predetermined threshold level. Thus, an appropriate threshold value may be set based on the actual S/N ratio in the optimum frequency band.
The speaker existence judging unit may judge the existence of the speaker based on the signal level in the optimum frequency band when the level of the environmental noise is larger than a predetermined reference level, and may judge the existence of the speaker based on the signal level of all frequency bands when the level of the environmental noise is smaller than the predetermined reference level. By this, when the environmental noise is large, the test signal of the optimum frequency band is used to accurately judge the speaker existence. When the environmental noise is small, not only the optimum frequency band, the test signal of all frequency bands is used to quickly detect the speaker existence.
The test signal supplying unit may supply only a component of the test signal in the optimum frequency band to the output terminal. By this, it is possible to avoid that a person in the acoustic space feels uncomfortable due to the unnecessarily large sound by reproducing the component that does not contribute to the speaker existence judgment.
The test sound detecting unit and the environmental noise detecting unit may be integrally configured as a single acoustic detecting unit. Thus, the configuration needed for the speaker detection may be simplified.
According to another aspect of the present invention, there is provided a program storage device readable by a computer having an output terminal for outputting a signal to drive a speaker and tangibly embodying a program of instructions executable by the computer to control the computer to function as a speaker detecting device including: a test signal supplying unit for supplying the test signal to the output terminal; a test sound detecting unit, installed in an acoustic space in which the speaker is installed, for detecting a test sound corresponding to the test signal; and a speaker existence judging unit for judging whether or not a speaker is connected to the output terminal by comparing a signal level of the test sound, detected by the test sound detecting unit when the test signal supplying unit supplies the test signal to the output terminal, with a predetermined threshold level.
According to still another aspect of the present invention, there is provided a computer data signal embodied in a carrier wave and representing a series of instructions which causes a computer, having an output terminal for outputting a signal to drive a speaker, to function as a speaker detecting device including: a test signal supplying unit for supplying the test signal to the output terminal; a test sound detecting unit, installed in an acoustic space in which the speaker is installed, for detecting a test sound corresponding to the test signal; and a speaker existence judging unit for judging whether or not a speaker is connected to the output terminal by comparing a signal level of the test sound, detected by the test sound detecting unit when the test signal supplying unit supplies the test signal to the output terminal, with a predetermined threshold level.
By reading the program into computer and executing it, the computer may function as the above-described speaker detecting device.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below.